Partition by in MYSQL|mysql over partition by row_number| Sql row number.

PARTITION BY Clause

When you specify a column or set of columns with PARTITION BY clause then
it will divide the result set into record partitions and then finally ranking functions 
are applied to each record partition separately and the rank will
restart from 1 for each record partition separately.

SQL SERVER

select  ROW_NUMBER() OVER(PARTITION BY  transactionHead
order by transactionHead) AS Row1,
TransactionHead from TransactionHeadbalance order by code

MYSQL code should look like..

SELECT 
@cur:= IF(TransactionHead=@id, @cur+1, 1) AS RowNumber, 
@id := TransactionHead FROM TransactionHeadbalance 
CROSS JOIN (SELECT @id:=(SELECT MIN(TransactionHead) FROM 
TransactionHeadbalance), @cur:=0) AS init 
ORDER BY TransactionHeadbalance.TransactionHead

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